Micro-mirror devices are well known and often referred to as micro-electromechanical systems (MEMS). Such micro-mirror devices have been formed on insulators or other substrates using commonly known micro-electronic fabrication techniques, such as photolithography, vapor deposition, and etching. The micro-mirror device can be operated as a light modulator for amplitude and/or phase modulation of incident light. One application of a micro-mirror device is within a display system. As such, multiple micro-mirror devices are arranged in an array such that each micro-mirror device constitutes one cell or pixel of the display system.
One conventional micro-mirror device includes an electrostatically actuated mirror immersed in a gas. The mirror pivots or deflects on a hinge about a mirror axis to different predetermined positions for reflecting light at such predetermined positions. However, there is often a design dilemma with respect to the stiffness of the hinge. Specifically, a weak hinge is often desired for deflecting the mirror to a maximum deflected position, since the weak hinge requires less applied voltage to deflect the mirror. On the other hand, a stiff hinge allows the mirror to spring-back faster from one deflected position to another deflected position. The stiff hinge is favorable in overcoming the gas dampening and reducing the transition time or frequency of the mirror pivoting between different deflected positions. However, the stiff hinge requires a greater voltage for deflecting the mirror. In addition, this type of micro-mirror device, immersed in a gas, often has problems in the switching frequency or speed by which the mirror can pivot. In particular, the mirror often has a tendency to stick to the landing sites due to a variety of forces such as the van der Waals force generated by water vapor present on the device surface and intermetallic bonding. Such sticking directly reduces the switching frequency by which the mirror can pivot from one position to another.
Another conventional micro-mirror device includes an electro-statically actuated mirror immersed in a dielectric liquid. Although this type of micro-mirror device does not experience the same problems of sticking, the pivoting mirror experiences a fluidic dampening effect within the dielectric liquid. Such a dampening effect may result in loss of speed and frequency of the pivoting mirror, which causes limitations in the type of applications with which the micro-mirror devices can be implemented, and/or causes a corresponding time-delay by which images are clearly viewed in, for example, a display system.
Therefore, there exists a need in the art to increase the speed and frequency by which a micro-mirror device actuates.